With the addition of more home fiber optic services, fiber optic cables, such as telephone and internet access fiber cables, are commonly hung from telephone poles and extend to the houses which they service. These cables are typically hung using a variety of clamps such as P-clamps (having a shell bail shim and wedge component). These P-clamps assist in suspending the fiber cable by attaching the fiber cable to hooks located on the poles and on the house or apartment building.
These clamps transmit pressure on fibers within the fiber tubes in a fiber cable if the cable design is oval. Furthermore, the non-rectangular (flat) design may result in the wedge and shims of the clamp rolling or bending under the curves of the cable, causing the edges to pull away from the guide slots resulting in clamp failure.
Alternative flat cables are available, however, one major problem with this common flat design drop cable installation is that the fiber cable is subject to a high amount of tension between the two clamps in the span from the telephone pole to the house. Currently used flat drop fiber cable designs, typically sandwich the fiber portions of the cable between the strength portions of the cable. Such arrangements cause the fiber tube portion of the cable to be crushed when attached to the clamps, when tighter clamp tension is applied. This “loose sandwich” approach may result in minimal adhesion and coefficient of friction transfer to the strength members.
For example, as shown in FIG. 1(a)-1(f), prior art designs typically include a tube containing optical fibers surrounded by a jacket flanked on both sides by strength members. Also shown in FIG. 1(b), another prior art design includes additional strength members set off to the side of the cable. Some prior art arrangements shown in FIGS. 1(c) and 1(d) also employ yarns added around the rigid strength members in an attempt to add strength to the design. However, these yarns have the effect of further reducing the jacket's adhesion to the constituents, thereby reducing the efficiency of the clamp-fiber cable assembly.
Another drawback associated with the prior art designs shown in FIGS. 1(a)-1(f) is that they require that the jacket be applied loosely around the strength members so as not to lock in the tube too tightly. If the jacket is too loose in such designs, the fiber cable and clamp connection may fail with the jacket tearing away from the cable constituents underneath within the clamp or at the exit of the clamp.
Yet another drawback with the prior art designs as shown in FIGS. 1(a)-1(f) is that they require that an installer disassemble the strength portion of the cable in order to access the optical fibers. The center tube configuration of these prior art designs, where the tube containing the optical fibers is located centrally in between the strength members, requires that the cable be destroyed for mid-span access of the fiber.
As such, these prior art designs lack sufficient strength due to P-clamp space constraints and may fail within spans of, or in excess of, 150 feet in heavy wind and ice load.